diff --git a/src/configure.in b/src/configure.in
index b15eed07a3f1101c6995441bb176e12bcd3b4822..27a969e460a08156b7fde5f1237cf181c06898ce 100644
--- a/src/configure.in
+++ b/src/configure.in
@@ -1,4 +1,4 @@
-AC_REVISION("$Id: configure.in,v 1.163 1998/02/27 17:59:11 marcus Exp $")
+AC_REVISION("$Id: configure.in,v 1.164 1998/03/05 14:06:46 grubba Exp $")
 AC_INIT(interpret.c)
 AC_CONFIG_HEADER(machine.h)
 
@@ -175,6 +175,11 @@ case "$pike_cv_sys_os" in
        ;;
      esac
   ;;
+  SunOS*)
+    # gcc on SunOS 4 forgets to define this:
+    echo "SunOS. Adding -D__USE_FIXED_PROTOTYPES__"
+    CFLAGS="$CFLAGS -D__USE_FIXED_PROTOTYPES__"
+  ;;
   BSD/OS*)
     LD="$BINDIR/smartlink shlicc"
   ;;